Starters are often used in single-phase induction motors for driving, for example: refrigerator, air conditioner, and other enclosed compressors; this kind of starter is shown in FIG. 27 (A). The positive characteristic thermistor 312 is connected in series to an auxiliary winding S (energized by alternating-current power source 90 along with main winding M) connected in a parallel fashion with respect to auxiliary winding S. In such a starter, when starting up a single-phase induction motor 100, the positive characteristic thermistor 312 presents low electrical resistance, and a starting current flows in the auxiliary winding S. As a result of the starting current, the positive characteristic thermistor 312 becomes high in resistance, and the current to the auxiliary winding S is limited. As a result of this configuration during stationary operation (after completion of the starting of the single-phase induction motor), the positive characteristic thermistor 312 is applied with supply voltage and continues to generate heat by itself, though about 2 to 4 W of power is always wasted.
Upon stopping the conventional starter (single-phase induction motor 100), re-starting is difficult; this is due to the large thermal capacity the positive characteristic thermistor 312 has. Once reaching high temperature and high resistance during operation, it takes dozens of seconds to several minutes until it is ready to start again. If it attempts to start again before this lag time (as the positive characteristic thermistor 312 is high in resistance due to the undepleted heat), only a small current flows in the auxiliary winding S; therefore, the rotor of the motor 100 is confined. Concurrently, a large current flows through the main winding M, and the overload relay 50 is actuated to arrest the re-starting. The reset time of the overload relay is initially slightly shorter than the cooling period of the positive characteristic thermistor 312 to re-start. If the overload relay operates and resets repeatedly, the temperature becomes higher gradually, and the reset time is longer. As the reset time of the overload relay becomes longer than the cooling period of the positive characteristic thermistor 312, the motor 100 is ready to start. A similar phenomenon occurs in a compressor motor for a refrigerator: when the compartment temperature drops, the thermostat is cut off and the compressor motor stops; inversely, when the door is opened, the compartment temperature rises, turning on the thermostat. In such a case, not only does it take longer for re-starting, the life of the overload relay is subsequently shortened.
Accordingly, the present applicant previously proposed a starter for a single-phase induction motor with the structure as indicated in FIG. 27 (B) [Japanese unexamined patent publication No. H6-38467]. In the circuit, the bimetal 218 is provided in series to the positive characteristic thermistor 312 in the starter 210. By heating the bimetal 218, the current to the positive characteristic thermistor 312 is cut off. By resistance 214 reacting on smaller power consumption than the positive characteristic thermistor 312, the OFF state of the bimetal 218 is maintained, and power consumption is reduced. Further, Japanese unexamined utility model publication No. S56-38276 discloses a starter with the positive characteristic thermistor disposed in two divisions.
Further, the inclusion of the positive characteristic thermistor in the starter with the ease of mounting the single-phase induction motor, socket terminals may be provided to connect to the connection pins at the side of the single-phase induction motor. For example [as disclosed in Japanese unexamined utility model publication No. S62-115760]: three connection pins project from the single-phase induction motor; they are electrically connected by way of socket terminals on the starter.
Electrical devices receive much larger vibrations from the motor, as well as other outside forces. If the holding strength of the socket terminals is weak (i.e.: during dismounting for checking, reassembling after removal, etc.), the electric contact of the starter with the electrical devices may be insufficient. Particularly found in a starter for a large motor, the contact area is heated and terminal can be damaged. The starter may not function in these cases, allowing for the possibility of fire or other accident.
A plan view of the socket terminal incorporated in a conventional starter of prior art is shown in FIG. 28 (A), a sectional view in FIG. 28 (B), and a bottom view in FIG. 28 (C). This socket terminal 122 is connected to connection pin 212 as shown in FIG. 28 (F). In this arrangement, the stress by galling (galling force) mainly occurs in two directions X and Y. As a result, socket terminal 122A may not restore the original position due to effects of galling force as shown in FIG. 28 (G). Hence, the gripping force of connection pin 212 by socket terminal 122A is substantially lowered, and the contact resistance increases due to faulty contacts. When current flows, heat is generated, and damage of the terminal and other problems may occur.
To solve these problems, various patents have been proposed, such as Japanese unexamined patent publication No. H8-149770, and Japanese unexamined patent publication No. 2001-332159. Japanese unexamined patent publication No. H8-149770 proposes a tubular socket terminal with four grooves provided along the insertion and removal direction of the connection pin. Japanese unexamined patent publication No. H8-149770 also proposes a pair of junction tongues for absorbing stress if galling force occurs in the gripping portion. Japanese unexamined patent publication No. 2001-332159 proposes a bump for preventing the socket terminal from opening near the slit opening of the socket terminal.
However, in the starter disclosed in Japanese unexamined patent publication No. H6-38467, in order to maintain the OFF state of bimetal 218 by resistance 214, as compared with the circuit configuration in FIG. 27 (A), the power consumption is reduced to ⅓. Since the positive characteristic thermistor in Japanese unexamined utility model publication No. S56-38276 is divided into two sections, the power consumption can be reduced by half.
Similar to the power consumption in the starter of Japanese unexamined patent publication No. H6-38467 (the thermal capacity is large in resistance 214 for maintaining the OFF state of bimetal 218), the single-phase induction motor could not be re-started quickly. Since the positive characteristic thermistor is divided into two sections in Japanese unexamined utility model publication No. S56-38276, the re-starting time could be decreased only to half.
The invention is devised to solve the problems of the prior art; to present a starter for a single-phase induction motor capable of saving energy by substantially reducing consumption of power during stationary operation by using the positive characteristic thermistor.
The tubular socket terminal disclosed in Japanese unexamined patent publication No. H8-149770 is likely to be deformed by the stress on the arc portion divided by a groove. The socket terminal, with the junction tongues of Japanese unexamined patent publication No. H8-149770, has the junction tongues projecting sideways, problematically taking up too much space in the limited storage area of the starter. The socket in Japanese unexamined patent publication No. 2001-332159 has a bump formed separately from the socket terminal. Additionally, this also takes up much space and is hard to store in the starter.
The aforesaid invention is designed to solve these problems, and effect a starter of high reliability and long durability.